ManyMouse - Bluetooth, Touchpad, Touchscreen, virtual bindings

[Torinde]

Dosbox Staging dual mouse functionality that uses ManyMouse (icculus/manymouse/issues/3) doesn't support:

• Bluetooth mouse
• laptop touchpad

It would be nice as well to have support for:

• touchscreen
• use as "mouse" the physical keyboard keys
• use as "mouse" the physical gamepad/joystick

Related to dosbox-staging/dosbox-staging/issues/2066

Related request is (user customizable) any-to-any mapping between all physical/virtual input devices (mouse-as-joystick, touchscreen-as-joystick, keyboard-as-joystick, touchscreen-as-keyboard, etc.)